Extraction process



y 1935- I D. R. MERRILL ET AL 2,002,702

I EXTRACTION PROCESS Filed 001;. 24, 1952 2 Sheets- Sheet 1 I INVENTORJ flaviaRIVezri/l 451 /2171}: Jubl'ow ATTORNEY.

y 1935. DR. MERRILL El AL 2, ,7

EXTRACTION PROCESS Filed Oct. 24, 1932 2 Sheets-Sheet 2 I NTO f \l QaWUBMrrIYIPIZZ DJDZ tOW ATTORNEY.

Patented May 28, 1935 UNITED STATES EXTRACTION PROCESS David B. Merrill, Long Beach, and Philip Subkow,

Los Angeles, Calif., assignors to Union Oil Company of California, Los Angeles, (hill, 9. corporation of California Application October 24, 1932, Serial No. 639,343

14 Claims.

This invention relates toa process for the production of lubricating oil. More specifically it relates to a process for the production of lubricating oil from petroleum by the use of solvents. One of the distinctive characteristics of a lubrieating oil is its viscosity. Its usefulness as a lubricant depends, at least in part upon its viscosity. For many purposes lubricants are desired whose viscosity will vary as little as possible with variations in temperature, i. e., have low temperature viscosity susceptibilities. Those fractions which exhibit a low temperature viscosity susceptibility are oftimes referred to as the paramnic oils whereas the fractions which exhibit a high temperature viscosity susceptibility are referred to as the non-parafiinic oils. The heavy oil fractions of many crude oils, from which lubricating oils are produced consist of a mixture of hydrocarbons some of which exhibit a low temperature viscosity susceptibility and some of which exhibit a high temperatureviscosity suspectibility. In order to produce 'sup'erior lubricating oil from hydrocarbon mixtures as described above, those oils present having a high viscosity temperature susceptibility are separated from the oils present which exhibit a low temperature viscosity susceptibility. Solvent extraction is one of the methods employed to separate the undesirable oil from the desirable oil. Solvents, such as aniline, furfural, nitrobenzene, selenium oxychloride, sulphur dioxide or B B dichlorethyl ether are capable, under the proper conditions of temperature and pressure, of dissolving the fractions present which are nonparafiinic in character.

, These solvents form relatively heavy solutions with the non-paraflinic oil fractions and can be separated from the insoluble parafiinic oil fractions by settling. The separated parafiinic oil fractions or rafilnates and nonparafiinic oil fractions or extracts dissolved insolvent are then distilled to separate the solvent from the oil. The paramnie fractions may then be given such further treatment as necessary to remove any remaining impurities. The non-parafiinic oil fractions being relatively valueless are utilized as fuel or as cracking stock in conversion processes. The separation of hydrocarbon mixtures into paraifinic and non-parafiinic fractions by the use of solvents is. not restricted to batch operation but may be carried out in a continuous manner. Where continuous extraction is employed it is customary to fiow the solvent oounter-.

currently to the oil to be extracted. Hence the oil being purified is progressively being contacted with solvent which is less contaminated with nonparamnic fractions. The oil entering the extraction system is contacted with solvent containing a relatively high concentration of non-paramnic fractions whereas the purified oil is finally contacted with pure solvent. In this manner the maximum degree of refinement is usually obtained because at the final stage of the extraction relatively pure oil is contacted with fresh solvent which has a high selective solvent power to reparate the parafiinic and non-paraflinic fractions because it is not contaminated with non-parafllnic oil. When continuous countercurrent extraction is employed the extraction step may be carried out in one stage wherein the solvent and 15 oil flow countercurrently or it may be carried out in a plurality of stages wherein the extracts obtained from the later stages of the process are returned to the earlier stages of the process and employed therein as the extracting medium. Thus in the first extraction stage the oil to be extracted is contacted with solvent containing dissolved fractions from a later stage. The insoluble oil portion in the first stage passes to the second stage where it is contacted with solvent containing less of the extracted fractions. The insoluble oil from the second stage passes successively in the same manner as described above, to the remaining extraction stages until it reaches the final stage wherein it is extracted with pure solvent. In processes of this character the same temperature is employed throughout the system and as final products there are obtained a fraction consisting largely of the non-paraflinic fractions and a fraction which is in the main composed of the paraffinic fractions.

. We have found it desirable to extract oil containing hydrocarbons of the paraflinic and nonparaffinic type, with a solvent, in a plurality of stages in which fresh solvent is added in each successive stage and to separate from each stage a rafiinate and solvent containing dissolved fractions. The solvent containing dissolved fractions is cooled to a temperature sufficiently low to cause the most insoluble fractions present to be forced out of solution. This mixture is then passed into a decanting chamber where the insoluble fractions, owing to their relatively low specific gravity rise to the top of the settling chamber, are removed therefrom and introduced into the lower zone of the next succeeding column. The solvent and dissolved fractions introduced into the settling chamber have a relatively high specific gravity and readily settle out. This fraction is introduced into the intermediate zone pipe I.

of the next succeeding extraction column or as a further modification the solvent and dissolved fractions may be divided into two streams. One stream may be introduced into the intermediate zoneof the nextsucceeding extraction column and the other stream may be returned to the inter- .mediate zone of the preceding extraction'column from which it w8s obtained. After extracting an oil to produce an extract phase soluble in the selective solvent and after cooling the extract phase to cause separation of the most insoluble fractions from the solvent and fractions remaining dissolved, these insoluble fractions and fractions remaining dissolved in the solvent are contacted in a subsequent extraction in the manner set forth above, in order that the said insoluble fractions may function as a wash oil to remove valuable constituents of the low solubility paraf- "and solvent containing dissolved fractions; to

cool the solvent solution of extracted fractions and separate oil fractions therefrom; to introduce the oil separated by cooling the solvent into the lower zone of the next succeeding extraction stage and to introduce the cooled solvent-containing the remaining dissolved fractions into the intermediate zone of the next extraction stage.

Furthermore, it is an object of our invention to extract hydrocarbon mixtures containing parafflnic and non-paraflinic fractions in a plurality of stages in which fresh extracting medium is introduced in each successive stage and there is withdrawn therefrom a ramnate and solvent containing dissolved fractions. The solvent containing the dissolved fractions is cooled to separate oil fractions insoluble in said solvent at the lowered temperature. The cooled solvent and undissolved fractions are separated, the insoluble fraction is introduced into the lower zone of the next succeeding extraction stage and the solvent and remaining dissolved fractions are directed into twostreams, one of which is introduced into the intermediate zone of the next succeeding stage.

and the other stream is returned to the intermediate zone of the preceding extraction stage.

Figure 1 is a schematic arrangement of one form of apparatus which we may employ to carry out our process.

Figure 2 is another schematic arrangement of apparatus which we may employ to carry out our process.

Referring more particularly to Figure 1, extracting medium, from a source not shown, is introduced into the upper zone of column 3 through The raw stock to be extracted is introduced into the lower zone of column 3 through I pipe 2. The extracting medium in column 3 being heavier than the raw stock passes downward through theascending column of oil. In its passage downward through the oolumn 3 the extracting medium dissolves certain non-parafflnic hydrocarbons present'in the oil. The oil from which the non-parafiinic fractions have been removed isremoved from column 3 through line 4 as a first rafflnate.

The solvent and dissolved fractions a e removed from the lower zone of column 3 through line 5, valve 3, line I, pump 8 and line 8 to cooler 4| where the temperature of the solvent and dissolved fraction is lowered suihciently to cause a portion of the dissolved fractions to be forced out of solution. The cooled mass in cooler 4| is then passed through line l to settling chamber-H where the-light insoluble fractions rise to the top, are removed through line'll and are introduced into the lower zone of extraction column l8.- The relatively heavy solvent containing the remaining dissolved fractions is removed from the bottom of settling chamber II through line l2, valve'l3, line H, pump l5 and line" and then introduced into the intermediate zone of column l3. tion in column I 8 is relatively lower than the temperature in column 3.

Fresh solvent is introduced into the upper zone of column I8 through line IS. The temperature of this solvent is usually approximately the same as that of the fractions introduced into the column through lines l6 and II. The descending heavy solvent in column l8 dissolves a portion of the fractions in the ascending column of oil which finally rises to the top of the column and is removed through line 20 as a second: ramnate.

The solvent and dissolved fractions settle to the bottom of column l8 and are removed through line 2|, valve 22, line 23, pump 24 and line-25 to cooler 28 where the temperature of this solution is lowered sufliciently to cause a portion of The temperature of extracthe hydrocarbons to be forced out of solution.

The cooled mass incooler25 is then passed through line 27 to settling chamber 28 where the insoluble relatively lightoil fractions rise to the top, are withdrawn through line 29 and introduced into the lower zone of column 30. The solvent con taining the remaining dissolved fractions settles out in chamber 28 and is passed through line 3|, valve 32, line 33, pump 34 and line 35 into the intermediate extraction zone of column 30.

Fresh solvent is introduced into the upper zone of column 30 through pipe at a temperature substantially the same as that of the fractions introduced into column 30 through lines 28 and 35.

The relatively heavy solvent in column 30 gravitates downward through the ascending column of oil. In its path downward the solvent dis solves certain non-paraflinic fractions from the oil. The purified oil finally rises to the top of column 30 and is removedas a third raflinate through line 36. The solvent containing dissolved fractions is removed' fromcolumn '30 through line 31, valve 38 and line 39 to distillation means where the solvent isrecovered from the extract. The raflinates recovered from lines 4, 20 and 33 are also distilled to remove any re and 35 aid the fresh solvent introduced through lines l9 and 40 in removing non-parafil'nic oils from the ascending column of oil introduced into the lower zones of these columns.

Referring more particularly. to Figure 2, the stock to be extracted enters column 52' through line 50. The extraction medium enters column 52 through line 5|. The relatively' heavy solvent passes downward through the ascending column of relatively light-oil. During its passage downward through column 82 the solvent dissolves the most soluble fractions present. The ascending column of oil finally rises to the top of the column and is removed as a first ramnate through line 58. The solvent containing dissolved fractions is removed through line 84, valve 88, line 56, pump 81 and line 88 to cooler 88 where its temperature is lowered sufiiciently to cause a portion of the dissolved oil to be forced out of solution. The cooled mass in cooler. 88 then passes through line 88 to settling chamber 8| where the relatively light insoluble oil fractions rise to the top and are conducted through line 82 'into the lower zone of extraction chamber 88. The solvent containingithe remaining dissolved fractions is removed !rom settling chamber through line 84. From line 84 the stream of solvent and dissolved fraction is divided; one stream passes through valve 18, pump H and line 12 and is introduced into the intermediate zone of extraction column 83. The other stream passes through valve 8!. pump 66, and line 81 into heater 88 where its temperature is raised substantially equal to that of the stock and solvent introduced into column 52 through lines 50 and 8!. From heater 88 the solvent passes through line 89 into the intermediate zone of extraction column 52.

Fresh solvent is introduced through line 14 into column 83 at a temperature substantially the same as that of the oil and extraction medium 'entering this column through lines 62 and I2.

The fresh solvent, along with the partially contaminated solvent in column 68 move downward through the ascending column of oil and dissolve a portion of the undesirable components present. The ascending column of oil in column 83 finally is removed through line I3, as a second raflinate.

The solvent containing dissolved fractions is removed from column 63 through line 15, valve 16, line 11, pump I8 and line I8 to cooler 80 where its temperature is lowered sufliciently to cause separation of a portion of the dissolved oil. The cooled mass then passes from cooler 80 through line 8| into settling chamber 82, where the relatively light insoluble fractions rise to the top and are removed through line 88 into the lower zone of extraction column 84. The relatively heavy solvent containing the remaining dissolved fractions settles out of chamber 82 and is removed through line 85. Here the solvent and remaining dissolved fractions are divided into two streams. One stream passes through valve 86, pump 92 and line 93 into the intermediate zone of extraction column 84. The other stream is removed through valve 81, pump 88=and line 88 into heater 9!! where its temperature is raised to a point substantially the same as that of the solvent entering chamber 63 through lines 12 and T4. The heated solvent containing dissolved fractions then passes from heater 9!! through line 81 into the intermediate zone of column 63. The material introduced through line 9| into extraction column 63 is less contaminated with dissolved-fractions than the material introduced in this column through line 12. Furthermore, the material introduced into column 63 through line I2 is a contaminated solvent with respect to the solvent introduced'through line 14. These three solvents introduced through lines l4, l2 and 9|, respectively, countercurrently contact therising column of oil introduced through line 82 in the inverse order of their degree of purity, i. e., the oil is contacted with the most contaminated solventfirst and finally with fresh solvent. Likewise the rising oil column in column 82 introduced through line 81 is contacted first with contaminated solvent introduced through line 88 and iglnally with fresh solvent introduced through ine 0.

Fresh solvent is introduced through line 88 into the upper zone of column 84 at a temperature substantially the same as the oil fraction introduced into this column through line 83 and the contaminated solvent introduced through line 83.

The ascending column of oil in column 84 is first contacted with the contaminated solvent introduced through line 83 and finally with the fresh solvent introduced through line 88 after which it is removed through line .94 as a third rafllnate. The solvent containing the dissolved fractions is removed from column 84 through line 85, valve 98 and line 91 to distillation means, not shown, where the extract is separated from the solvent. h

The rafllnates "recovered through lines 53, I3

and 84 may be given any further treatment necessary for the production of finished oils; such 'as acid, alkali and/or clay treatment.

introduced into'column 8 through line 2 at an approximate temperature of 110 F. B '3' dichorethyl ether is introduced into the upper zone of column 3 through'line l at a temperature of about 110 F. A first railinate is withdrawn from column 3 through line 4. Solvent containing dissolved fractions is withdrawn from the bottom of column 3 through line 5 and passed through cooler 4| where its temperature is lowered to approximately 80 F. The cooled mass then passes from cooler 4i to settling chamber II where the oils forced out of solution by cooling rise to the top and are introduced into the lower zone by column l8 through line H. The solvent containing the remaining dissolved fractions is withdrawn from the bottom of chamber II and introduced into the'intermediate zone of extraction column 18. B B dichlorethyl ether is introduced into column l8 through line 19 at a tem-, perature of about 80 F. A second raflinate is withdrawn through line 20 from column I8. The B B diclorethyl ether containing dissolved fractions is withdrawn from column l8 through line 2| and passed to cooler 26 where its temperature is lowered to approximately 40 F. At this temperature a portion of the dissolved oil is rendered insoluble. The cooled mass passes from cooler 28 to settling chamber 28 where the relatively light insoluble oil rises to the top and is withdrawn through line 29 and introduced into the lower zone of extraction column 30.

The solvent containing the remaining dissolved fractions settles to the bottom of chamber 28, is withdrawn and introduced through line into the intermediate zone of column 30. B B dichlorethyl ether at a temperature of about F. is introduced through pipe 40 into. the upper zone of column 30. The oil introduced in column 30 through line 29 rises and is countercurrently extracted by the stream of solvent introduced through line 40 and the contaminated solvent introduced through line 35. The oil from which the undesirable fractions have been removed is finally withdrawn through line 36.

The solvent containing the dissolved fractions is removed through line 39 and sent to distillation means where the B B dichlorethyl ether is separated from the extracted fractions.

While the example is specifically directed to extraction in stages operating at successively lower temperatures it is to be understood that all of the extraction stages may be operated at the same temperature and in some cases it may be desired to operate each successive stage at an increasing temperature, especially where different solvents are introduced in the successive stages. v

When it is desired to operate all of the extraction stages at the same temperature or each successive extraction stage at an increasing temperature it then becomes necessary to interpose heaters in lines "5, i1, 28 and 35 of Fig. 1 and lines 62, 12, 83 and 83 of Fig. 2. By the use of these heaters the fractions passing to all of the extraction stages may be heated to the same temperature or if desired the temperature of the fractions passing to the successive extraction stages may be increased at each stage.

This same effect may be produced by closing valves i3 and 32 of Fig. l and passing the solvent and dissolved fractions to the respective extraction stages l8 and 30, in which case coolers 4| and 26 merely function as flow lines and the solvent and dissolved fractions pass to each successive extraction stage at substantially the same temperature. Whenit is desired to operate each fractions withdrawn from column 8 are increased in temperature before passing via line 29 into column 30. When M and 29 of Fig. 1 function as heaters, valves l6 and 32 remain closed.

The same solvent may be employed in each successivestage of the extraction or if desired .difierent solvents may be introduced in each successive stage as for example in Figure 1 the initial solvent introduced through line I may be liquid sulphur dioxide, the solvent introduced in lines l9 and 40 may be B B dichlorethyl ether or any other solvent which will separate the types of raflinates desired in each of the successive stages.

The foregoing example is merely illustrative of one method of carrying out our invention and is not to be construed as limiting the invention which we claim.

We claim:

1. A process for separating a hydrocarbon oil mixture into aplurality of fractions which comprises extracting said oil with a solvent into an insoluble fraction and fractions dissolved in said solvent, separating the insoluble fraction from the fractions dissolved in said solvent, cooling said solvent containing dissolved fractions to separate a fraction insoluble in said cooled solvent, removing said insoluble fraction from said cooled solvent containing the remaining dissolved fractions,

mixture into a plurality of fractions which comprises extracting said oil with a solvent into a fraction insoluble in said solvent and fractions soluble in said solvent, separating said insoluble fraction from said solvent and dissolved fractions, cooling said solvent and dissolved fractions to separate a further fraction, removing said last mentioned fraction from said cooled solvent containing the remaining dissolved fractions, subsequently passing said fraction separated from said cooled solvent to a later extraction stage, and extracting said fraction passed to said later stage with said cooled solvent containing the remaining dissolved fractions.

3. A process for separating a hydrocarbon oil mixture into a plurality of fractions which comprises extracting said oil with a solvent into a fraction insoluble in said solvent and fractions soluble in said solvent, separating said insoluble fraction from said solvent and dissolved fractions, cooling said solvent and dissolved fractions to separate a further fraction, removing said last mentioned fraction from saidcooled solvent containing. the remaining dissolved fractions, subsequently passing said fraction separated from said cooled solvent to a later extraction stage, and extracting said fraction passed to said later stage with fresh solvent and said cooled solvent containing the remaining dissolved fractions.

4. A process for separating a hydrocarbon oil mixture into a plurality of fractions which comprises extracting said oil with a solvent, separating a fraction insoluble in said solvent from the solvent and remaining dissolved fractions, cooling the solvent containing dissolved fractions to separate a fraction insoluble in said cooled solvent, removing said insoluble fraction from said cooled solvent containing the remaining dissolved fractions, subsequently passing said fraction insoluble in said cooled solvent to a later extraction stage and extracting said cooled insoluble fraction with fresh solvent and said cooled solvent containing remaining dissolved fractions.

5. A process for separating a hydrocarbon oil mixture into a plurality of fractions which comprises extracting said oil with a solvent, separating a fraction insoluble in said solvent from the solvent and remaining dissolved fractions, cooling the solvent containing remaining dissolved fractions to separate a fraction insoluble in said cooled solvent, removing said insoluble fraction from said cooled'solvent containing the remaining dissolved fractions, subsequently passing said fraction insoluble in cooled solvent to a later extraction stage, extracting said cooled insoluble fraction in said later stage with fresh solvent and a portion of said cooled solvent containing dissolved fractions, heating the remaining portion of cooled solvent and dissolved fractions and returning said heated solvent and dissolved fraction to an earlier extraction stage.

6. A process for the separation of oil from a selective solvent containing dissolved fractions which comprises cooling said solvent and dissolved fractions to separate a fraction insoluble in said cooled solvent, removing said insoluble fraction from said cooled solvent containing the remaining dissolved fractions, passing said insoluble fraction separated from said cooled solvent and remaining dissolved fractions to a later extraction stage and extracting said insoluble fraction passed to said later stage with said cooled solvent containing the remaining dissolved fractions.

7. A process for the separation of oil from a selective solvent containing dissolved fractions which comprises cooling said solvent and dissolved fractions to separate a fraction insoluble in said cooled solvent, removing said insoluble fraction from said cooled solvent containing the remaining dissolved fractions, passing said insoluble fraction separated from said cooled solvent and remaining dissolved fractions to a later extraction stage and extracting said insoluble taining the remaining dissolved fractions, passing said fraction insoluble in cooled solvent to a later extraction stage, extracting said cooled insoluble fraction in said later stage with a portion of said cooled solvent containing dissolved fractions and returning the remaining portion of cooled solvent and dissolved fractions to an earlier extraction stage.

9. A process for separating a hydrocarbon oil mixture into a plurality of fractions which comprises extracting said oil with a solvent, separating a fraction insoluble in said solvent from the solvent and the remaining dissolved fractions, cooling the solvent containing the remaining dissolved fractions to separate a fraction insoluble in said cooled solvent, removing said last mentioned insoluble fraction from said solvent containing the remaining dissolved fractions, passing said fraction insoluble in cooled solvent to a later extraction stage, extracting said cooled insoluble fraction in said later stage with fresh solvent and a ,portionof said cooled solvent containing dissolved fractions and returning the remaining portion of cooled solvent and dissolved fractions to an earlier extraction stage;

10. A process for the separation of oil from a selective solvent containing dissolved fractions which comprises cooling said selective solvent containing dissolved fractions to separate a fraction insoluble in said cooled solvent, removing said insoluble fraction from the cooled solvent and remaining dissolved fractions, passing said insoluble fraction to a later extraction stage, ex-

tracting said cooled insoluble fraction in said later stage with a portion of said cooled solvent containing dissolved fractions and returning the tracting said cooled insoluble fraction in said later stage with fresh solvent and a portion of said cooled solvent containing dissolved fractions and returning the remaining portion, of cooled solvent and dissolved fractions to an earlier extraction stage.

12. A process for the separation of oil from a selective solvent containing dissolved fractions which comprises cooling said selective solvent containing dissolved fractions to separate a fraction insoluble in said cooled solvent, removing said insoluble fraction from the cooled solvent and remaining dissolved fractions, passing said insoluble fraction to a later extraction stage, extracting said cooled insoluble fraction in said later stage with fresh solvent and a portion of said cooled solvent containing dissolved fractions,

heating the remaining portion of cooled solvent and dissolved fractions and returning said heated solvent and dissolved fractions to an earlier extraction stage.

13. A process for separating .a hydrocarbon oil mixture into a plurality of fractions which comprises extracting said oil with a selective solvent,

separating a fraction insoluble in said solvent from the selective solvent and dissolved fractions, commingling said selective solvent and dissolved fractions with a wash oil and removing the, wash oil containing dissolved fractions from said sol-i vent and fractions remaining dissolved therein.

14. A process according to claim 13 wherein the wash oil is a fraction separated as an insoluble fraction from the selective solvent solution of dissolved oil fractions by cooling said solution and separating said fraction insoluble at the lowered temperature.

DAVID R, MERRILL.

PHILIP SUBKOW. 

